BMI Calculator for Adults
Enter your height and weight. You get your BMI, the adult category it falls in and the weight range that matches a healthy BMI for your height.
Calculated in your browser. Nothing you type is sent anywhere.
- Category
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- Healthy weight for your height
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- Compared with that range
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- BMI Prime (BMI / 25)
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What BMI is
Body mass index compares your weight with your height. It was developed in the 1800s as a way to describe populations, and today doctors and public health agencies use it as a fast screening tool. A single number cannot say whether a person is healthy, but it can flag a weight that may deserve a closer look.
BMI = weight (kg) / height (m)2
BMI = 703 x weight (lb) / height (in)2
Worked examples
- US units: 5 ft 9 in (69 in) and 160 lb. 703 x 160 / 692 = 112,480 / 4,761 = 23.6, which is in the healthy range. For that height, a healthy weight is about 125 to 169 lb.
- Metric: 175 cm and 70 kg. 70 / 1.752 = 70 / 3.0625 = 22.9. The healthy range for 175 cm is 56.7 to 76.3 kg.
Adult BMI categories
| BMI | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to 24.9 | Healthy weight |
| 25.0 to 29.9 | Overweight |
| 30.0 to 34.9 | Obesity, class 1 |
| 35.0 to 39.9 | Obesity, class 2 |
| 40.0 and above | Obesity, class 3 |
Healthy weight range by height
| Height | Healthy range (BMI 18.5 to 24.9) |
|---|---|
| 5 ft 0 in | 95 to 127 lb |
| 5 ft 4 in | 108 to 145 lb |
| 5 ft 8 in | 122 to 164 lb |
| 6 ft 0 in | 136 to 184 lb |
What BMI does not tell you
- Muscle versus fat. Strength athletes can have a BMI in the overweight range with little body fat.
- Where fat is stored. Fat around the waist carries more health risk than fat on the hips and thighs. Waist circumference and waist-to-height ratio add useful detail.
- Age, sex and ethnicity. Body composition changes with age, and some groups face higher risk at a lower BMI.
- Children and teens. Their BMI is judged against growth charts, not the adult cut-offs.
Talk to a doctor about your weight and health, especially if you are pregnant, very active, over 65, or have a medical condition. If you need to convert between feet and centimeters or pounds and kilograms, use the unit converter.
Frequently asked questions
How is BMI calculated?
BMI is weight in kilograms divided by height in meters squared. In pounds and inches, multiply weight by 703 and divide by height squared. A person who is 5 ft 9 in and 160 lb has a BMI of 23.6.
What is a healthy BMI?
For adults, a BMI from 18.5 to 24.9 is classed as a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obesity, with further classes at 35 and 40.
Is BMI accurate?
It is a quick screening number, not a diagnosis. It does not separate muscle from fat or show where fat is carried, so athletes and very muscular people can score high, and older adults with low muscle can score in the healthy range. Waist size and health checks give more detail.
Does this work for children?
No. For children and teens aged 2 to 19, BMI is compared with percentiles for the same age and sex. Use the CDC growth charts or ask a paediatrician.
Are the categories the same for all ethnic groups?
The standard cut-offs above are used in the US and the UK. Some health bodies recommend lower thresholds for people of South and East Asian descent, because health risks can rise at a lower BMI.
This calculator is for general information and screening only. It is not a diagnosis or medical advice. Talk with a doctor or other qualified clinician about your health. How we calculate and where numbers come from. Last reviewed October 2026.